The Second Law of Thermodynamics
by Cartographical
Summary: In the end, we'll all end up at room temperature. "Hunt" post-ep.


A sharp knock reverberates through the room.

"Kate," she hears, the word muffled through the bathroom door.

Fuck.

She gulps, swallows, presses the heels of her hands hard against her eye sockets until the blackness consumes her for a brief and blissful heartbeat.

"Be out in a second," she calls, wincing at the rough gravel of her voice, the low scrape of the words over her larynx.

"I'm coming in."

"In the bath," she replies, like that's somehow ever been a deterrent for him.

"I know," he says, and then he's opening the door like it's no big deal and she's cursing her idiotic self for failing to perform the infinitely simple maneuver of flipping the fucking latch.

She tries to look like she wasn't just in the midst of convulsively sobbing. "How's Alexis?" she murmurs.

He walks right over to her, flops down on the floor next to the tub, wraps his arms around his shins. "Good. Napping on the couch in front of _Star Wars_. Mother's still cooking."

"S – Something good?" she asks, curses the crack of her voice at the front of it.

"Kate," he says again, sounding like he's chastising, like he's actually fucking chastising her.

She pastes what she hopes is a reasonable smile onto her face. "What's up?"

His cheeks are pale. There are dark circles under his eyes. "Kate," he says again, reaching up and in, touching a finger to her knee and then flinching sharply away. Of course. "You're freezing."

"Thermodynamics is a bitch," she rasps. She wasn't cold before, but the light brush of his warm thumb against her knee has relit her nervous system. She suddenly can't seem to stop shivering.

He blinks at her, looking exhausted, looking like the shattered pieces of his heart are finally just starting to stitch themselves back into some semblance of order, and she can't even be angry with him for the places deep inside her that are still raw, still broken.

He nudges his fingers back into her, covering her knee with his palm, running his thumb in slow and steady circles over her the ridge of her patella. His hand is warm enough to burn, hot enough to brand. She can't help the brief and fervent wish that flares deep inside her, the horrible desire for him to just leave her in her cold and silent cocoon.

"I'm all for science, Beckett, and you know how I feel about experiments, but maybe it's time to get out of the bath? I think we've established a pretty firm understanding of entropy here."

"In a minute," she says, the heat of his hand still too bright against the dark chill that will not leave her.

He blinks, tilts his head at her, gives her a long, gorgeously silent moment before he speaks again. "We walked in that door four hours ago, and near as I can figure, for about a quarter of that time you've been sobbing in the bathroom."

"Is that not normal?" Her voice is about an octave away from the light, breezy tone she was going for.

"Maybe we should talk about it?" he asks, his voice low, steady, so damn fatherly and compassionate that it fists inside her chest, wraps its iron fingers around her lungs and will not release.

"Seriously?" The word slips out before she can corral it.

"You're mad I didn't call," he says.

A renegade sob tries to claw its way out of her throat, and she only just manages to choke it down. A tiny strangled noise escapes. "I'm not mad," she finally gets out.

The look in his eyes is so bleak. His hand doesn't leave her.

"I thought you were dead," she finally says, her breath steadier now. "I heard a gunshot – or, well, what I thought was a gunshot, and what the tech guys confirmed was probably a Heckler & Kock HK121, about seven minutes after I sprinted down there."

He blinks at her. "You brought it to tech?" is all he manages to ask.

She's fairly certain he does not understand. "I thought you were dead," she says, and that should be enough, those five words, but he's still looking at her with the soft kind of focus that she hopes – she _prays_ – means he's still not comprehending. "I brought it to tech because part of me – a big part of me – thought we were going to need to analyze the noise of the gunshot to figure out your murder weapon. Comb through the background to narrow down where your body might be buried. I booked a flight to Paris. I took a cab home. Got my passport – didn't really think to get anything else. Got back in the cab. Got out at La Guardia."

He understands now. His head is buried in his hands, his fingers clenched in tight fists on his forehead. "You didn't get on a plane," he rasps after too much silence.

"You called after I got through security," she says.

After he'd hung up she'd sat down on the cold tile in the middle of the concourse, crumpling with the sudden removal of her momentum. She'd sat and clutched her phone and breathed and tried not to think of all the people, her mom and Royce and Montgomery, all the people who chased after the things they had needed to chase and who had died because of it.

She sees the echo of those people, now, in the desolation in his eyes.

He understands.

"Second law of thermodynamics," she murmurs to him.

He shakes his head, staring at her like she's eviscerated him. She didn't want – this wasn't what she wanted.

She forces herself to lift a leaden arm, to cover his hand with her own. "Nowhere to go but forward," she says. He huffs, his face full of none of the quiet happiness he'd shimmered with when he and Alexis walked in the front door, and she has nothing to offer him to bring it back. "In the end, we'll all end up at room temperature."

"Some of us more than others," he says, failing miserably at the joke but gallantly wrapping a hand around hers anyway, tugging her up with one arm and reaching for a towel with another.

She's glad he doesn't apologize. There are no words that will fill the empty ache that settled in her chest when she'd been so sure he was dead, no reassurance that will outweigh the hollow void that rose within her as she pressed her passport into her stomach while standing in a long security line, as her brain spun off in so many different directions - the paperwork she would need to ship a body – two bodies? – back from Paris, the way she could shift her coffee table so that Martha could sleep in her bedroom and she could fit a mattress next to the couch.

"I won't do it again," he whispers as he wraps the towel around her shaking shoulders.

He can't make that promise. That laser-like focus, when it's on her, lights her up with the brilliance of its intensity, but it won't always be on her. She doesn't even want it always on her.

She thinks about the man who stands vibrantly alive in front of her, the girl who he rescued two doors away, sleeping on the couch, and she thinks that she can live with that knowledge, that the aching grief that will cling to her for weeks and weeks is a small price to pay.

He understands.

"I know," she says.


End file.
